Triphenylboron-amine compounds, and triphenylboron-pyridine (TPBP) compounds in particular, are known to be effective biocides and marine anti-fouling agents and are, therefore, commercially important products. See for example U.S. Pat. No. 3,211,679.
One method for making TPBP is by the reaction of TPBA with pyridine in aqueous solution. See JP 08311074 (the “JP 1074 Application”) and U.S. patent application Ser. No. 11/473,907 filed Jun. 23, 2006 (the “'907 application”), both incorporated herein by reference. Solid TPBP particles precipitate out when TPBA is reacted with pyridine.
However, after addition of pyridine to the aqueous TPBA, the resulting product slurry contains three moles of alkali (e.g., alkali metal hydroxide) for every mole of TPBP. Since the solubility of TPBP in an aqueous solution increases with increasing concentration of alkali, a considerable amount of the product TPBP is dissolved in the mother liquor.